Monophase and polyphase alternating-current machine.



No. 787,027. PATENTED APR. 11, 1905.

. M. VON DOLIVO-DOBROWOLSKY. MONOPHASE AND POLYPHASE ALTERNATING CURRENTMACHINE.

nrmonxox FILED MAY 1a. 1903.

2 sums-sum 1.

he by No. 787,027. 1 PATENTED APR. 11, 1905.

M. VON DOLIVO-DOBROWOLSKY. I

' MO-NOPHASE AND POLYPHASB ALTERNATING CURRENT MACHINE.

APPLICATION rum) MAY 18, 190a.

2 SHEETS-SHEET z.

UNITED STATES Patented April 11, 1905.

PATENT ()FFICE.

MONOPHASE AND POLYPHASE ALTERNATING-CURRENT MACHINE.

SPECIFICATION forming part of Letters Patent No. 787,027, dated April11, 1905.

Application filed May 18, 1903. erial No. 157,627.

To 1.7] whom it may concern Be it known that 1, MICHAEL voN Domvo-DOBROWOLSKY, a subject of the Russian Emperor, residing at Berlin,Prussia-German Empire, have invented certain new and useful ImprovementsRelating to Monophase and Polyphase Alternating-Gurrent Machines, ofwhich the following is a specification.

L. Maiche (German Patent No. 16,075) has already pointed out in the year1887 how the peculiarity of polarization elements having an aluminiumelectrode (unipolar cells) namely, that they allow only currentimpulsesof a determined direction to pass through may be utilized for thepurpose of exciting an alternating-current machine by its own current.That method, however alluringit was, has practically never been usedcommercially. This may no doubt have been due in part to theuneconomicalworking of the unipolar cells. This drawback might be remedied by meansof betterdesigned constructions of cells, as well in part by means ofmore favorable connections. Now the present invention specifies a modeof using the unipolar cells, in which the uneconomical working of thecells need scarcely be considered, for the reason that not the wholeamount of excitation, but only a portion thereof, is supplied by thecells. If as a matter of course only the extra amount of excitationwhich is required by an alternating-current machine working under a loadas compared with a machine not working under a load be taken from theunipolar cells, while the remainder of the excitation be taken in theusual manner from other sources of direct current, then it is clear thatthelow efficiency of the unipolar cell need hardly be taken intoaccount. 1V ith this arrangement the important advantage is attainedthat the excitation of the machine varies automatically with the amountof the load similarly to the so-called compound machines with direct orcontinuous current.

I shall now proceed to describe more fully some modes of connection andarrangements which explain the invention hereinbefore referred to.

In Figure 1, (1/ represents an alternatingcurrent machine which operatesthe mains Z).

In the main circuit of this machine a transformer a is interposed. Thesecondary current of this transformer is led through a unipolar cell (Zinto one of the two magnetwindings of the alternating-current machine,while the other of these magnet-windings is fed by an ordinary exciterw. The question whether the dimensions of these two windings are equalor different depends, among other things, on the amount of the fall ofpotential in the alternating-current machine.

In the arrangement illustrated in Fig. 1, as well as in the followingarrangements, the increase of excitation depends, however, only on theload increase in amperes and not on the extent of the displacement ofthe phases of the main current; but this drawback is practically of verylittle importance, as the so-called cos. is mostly maintained for a longtime at an approximately constant value. Slow variations of the same canoccasionally be adjusted by means of the regulating devices f and Fig.1.

In Fig. 1 a unipolar cell is simply interposed, whereby only half thenumber of the alternating current impulses are. utilized, and in somemeasure it is left to the great impedance of the magnet-winding toexpand this interruptedly-pulsating current into a constant continuouscurrent. However, other modes of connecting .the unipolar cells willfrequently be employed with advantage and by means of which a greateruniformity is attained. Thus, for example, the known (irraetz bridgeconnection of the cells, as illustrated in 2, or a somewhat simpler one,as illustrated in Fig. 3, or any other one may be employed. Furthermore,it is not at all necessary to interpose the regulating devices f and rin the manner illustrated in Fig. 2, as this is only one of the manynumerous possible ways of adjusting at will the potential of themachine, as well as the degree of dependence of the same on the load.Thus the regulating device f, instead of being connected in parallelwith the magnets, may also be connected in parallel with the secondaryor even with the primary of thetransformer, or it may also be connectedin series with the magnet-winding, and so on. Instead of the regulatingdevice or, in addition to this latter, a regulating resistance may beincluded in the magnet-winding of the exciter.

The above-described arrangement, Fig. 1, is, as already mentioned, in acertain respect somewhat similar to the arrangement of mixed excitationin continuous-current machines in so far as also in this case twomagnet-windings are employed. This is, however, not at all necessary,because the additional exciter-circuit may be connected in series withthe circuit of the exciter proper, as illustrated in Figs. 4c and 5, byway of example. In this case the result of placing more load on the mainmachine will be to cause a corresponding increase of the electromotiveforce in the circuit of the magnet, so that an automatic increase of theexcitation takes place. No further explanation is required in order tounderstand that regulating devices may also be interposed here atsuitable points. These two principal methods are suitable for every kindof excitation of an alternatingcurrent machine, whether it be producedby an exciting-machine or by a transformer or whether the excitation bederived from continuous-current systems or accumulators and the like.

1 shall now proceed to describe a particular modification of the presentinvention which is only suitable for use with certain exciter-machines.This is illustrated in Fig. 6. in this case the additonalexciter-current is not led around the magnets of the alternating-currentmachine, but around the magnets of the exciter. Obviously the sameaction is attained thereby, although in the case of sudden variations ofload the magnetism may perhaps not follow on quite so quickly; but insuch a case the advantage is obtained that the unipolar cells have tofurnish very much less energy still than in the hereinbefore-mentionedexamples and that therefore the comparatively low efliciency of thesecells is of still less importance. In fact, assuming that the excitationof a onethousand-kilowatt machine under full load be about 1.5 per cent,equal to fifteen kilowatts, then the exciter which would have to producethese fifteen kilowatts would require about seven per cent. of this forits own excitation, in round numbers equal to one kilowatt. Theexcitation between the condition of running without load and that offull load is assumed to vary, say, in the proportion of one to two-2 0.,the excitation of the exciter without load is 0.5 kilowatt and with loadone kilowatt. Then the unipolar cells have only to supply the amount ofone kilowatt minus 0.5 kilowatt equal to 0.5 kilowatt; but as thisamount of energy amounts to only one-twentieth of one per cent. of theoutput of the alternating-current machine it is evidently quiteimmaterial whether it is obtained with a high or low efliciency. mannerof influencing the excitation of the energizer, as just described, asingle n'iagnetwinding may be employed instead of the two Imagnetwindings, if the additional excitercircuit be connected in serieswith the circuit of the exciter proper, Fig. 7.

It is to be understood that as regards the nature of the invention itdoes not matter how this energizing machine is constructed in otherrespects. It may be a shunt-machine or a main-current machine or anexternallyenergized machine, or it may be a transformer. Furthermore,several continuouscurrent machines may have a common exciter, and theymay conjointly influence it, if this should seem advantageous for anyreasons.

The invention is also not limited to monophase alternating-currentgenerators; but it may just as well and even with more advan tage beemployed with polyphase machines. In the latter case the influencing ofthe excita tion may be effected by one only of the mains or by a numberor by all of them. Thus Fig. 8 shows an example of this arrangement fora rotary current-machine.

The use of the unipolar cells as such for the excitation of machines, asalready mentioned in the introduction, is not at all claimed as novel.Similarly automatic influencing of the excitation (compounding) by meansof the main current without the use of unipolar cells is not novel,because already prior to this it has been solved in various ways. Theessential novelty is rather the utilization of the simplicity ofunipolar cells for the excitation of a dynamo in combination with theentrusting of only a portion of the total excitation (additionalexcitation) to the cells, whereby the influence of the low efliciency ofsaid cells is of less consequence.

What Iclaim as myinvention, and desire to secure by Letters Patent, is-

1. An arrangement for diminishing the l'all in potential in monophase orpolyphasc alternating-current machines, consisting of a source ofcontinuous current, a circuit in connection therewith, which circuit isalso in connection with the magnet-windings of the alternatingcurrentmachine, a transformer in the main circuit of the latter, and a unipolarcell in the circuit of the secondary current of the transformer which isalso connected with the magnet-windings of the alternating-currentmachine.

2. An arrangement for diminishing the tall in potential in monophase andpolyphase alternating-current machines, consisting of a source ofcontinuous current, a circuit in c0nnection therewith, said circuitbeing also in connection with one of the magnet-windings of thealternating-current machine, a transformer in the main circuit of thelatter, and a unipolar cell in the circuit of the secondary current ofthe transformer which is also con- Also in the 1 nected with the otherof the magnet-windings of the alternating-current machine.

3. An arrangement for diminishing the fall windings of the said sourceof continuous curin potential in monophase or polyphase alterrent.nating-currentmachines,consisting of a source In testimony whereof Ihave signed my name of continuous current, a circuit in connection tothis specification in the presence of two sub- 5 therewith, said circuitbeing also in 1connection scribing witnesses.

with the ma net-windin s of the a ternatin i current machine, atranzformer in the main MICHAEL VON DOLWO'DOBROWOLSKL circuit of thelatter, and a unipolar cell in the Witnesses: circuit of the secondarycurrent of the trans- ROBERT KUHNEL, IO former, which is connected withthe magnet- ERNST HoLu.

